The onetime courtroom adversaries who toppled California's ban on same-sex marriage expect the U.S. Supreme Court to resolve the marriage issue nationwide within a year - and, once again, they're predicting victory.

From all current trends, "there's only one outcome": a ruling declaring a constitutional right to wed one's chosen partner, regardless of sexual orientation, attorney Theodore Olson told a Commonwealth Club audience in San Francisco on Thursday evening.

It was the first anniversary of the Supreme Court's ruling that effectively allowed gays and lesbians in California to marry. Olson and David Boies - antagonists in the Bush vs. Gore case that decided the 2000 presidential election - teamed to represent two couples and a newly formed gay rights group in a challenge to Proposition 8, the 2008 California initiative that restricted marriage to opposite-sex couples.

In the end, they won when the Supreme Court dismissed a final appeal by Prop. 8 sponsors without ruling on the constitutionality of same-sex marriage itself.

Another ruling the court issued the same day, overturning a ban on federal benefits for married same-sex couples, has been invoked since then by more than a dozen federal judges to strike down state laws that banned same-sex marriages or refused to recognize marriages performed elsewhere.

The states include Virginia, where Olson, a former Justice Department official under Bush and Ronald Reagan, and Boies, a liberal Democrat, represent gay and lesbian couples seeking the right to marry. A federal appeals court heard arguments in the case last month. On Wednesday, another appeals court, in Denver, became the first to declare constitutional marriage rights for same-sex couples when it overturned a law in Utah.

"We cannot live in a country with a patchwork of laws," Olson said Thursday, noting that almost half the U.S. population now lives in states where same-sex marriage is legal. "The Supreme Court of the United States has got to take this case," and both he and Boies believe "it's going to happen in the next term."

The Prop. 8 suit faced widespread opposition from gay rights groups, which preferred state-by-state campaigns and feared a defeat in the conservative Supreme Court that would set back the movement for decades.

The two lawyers address the criticism in their new book, "Redeeming the Dream: The Case for Marriage Equality," saying they had been unwilling to ask gays and lesbians to await acceptance from conservative states or changes in the court, a process that could have taken decades.

Another reason, Boies said Thursday, was that "there are a lot of lawyers in California" and a federal lawsuit was inevitable. He said he and Olson had experience and resources available to few other lawyers, with more than 50 attorneys and paralegals from their two firms working on the suit as it moved from a trial in San Francisco to an appeals court and to the Supreme Court.

"This was the right case at the right time, and we were the right people," Boies said.